The present invention relates to a hub, which is especially suitable for bicycles.
In addition to bicycles, the hub can be used for other purposes, for example for all types of towing trailers, especially bicycle trailers, for wheelchairs and other such similar contrivances. For the sake of simplicity, however, the invention will be described in the following with reference to its use with bicycles, whereby said description shall not be construed in any way as a limitation of application.
Hubs of the type referred to here serve to connect the stationary wheel axle with the freewheel rotating about said axle. The connection between the hub and the rim of the wheel is made with steel spokes, whereby generally between 24 and 36 spokes are used which are inserted into bores on the hub and the rim in adherence to a given pattern. In addition to said spokes, connections today are increasingly making use of just a small number of, for example, three or four plastic supports, or employing discs such as carbon discs.
High demands are placed on hubs especially with wheels used for sporting purposes, most particularly with wheels used during competitive events. On one hand, a hub should rotate with the least amount of frictional drag possible and on the other hand, it should enable a support as free of play as possible, it should exhibit only slight soiling and wear, and it should be easy to mount and disassemble.
Generally, it is the rear wheel of a bicycle which is driven. To this end, in addition to the actual hub housing, a rotor or driver is also arranged on the rear wheel hub axle, to which one or more gearwheels or sprocket wheels can be firmly mounted in order to transfer the driving force to the rear wheel.
To prevent the front pedal crank from continuing to rotate during a downhill ride, a freewheel is usually integrated into the rear hub, which transfers the driving force of the driver or the rotor from the rotor to the hub housing and thus to the rear wheel while having the effect that the hub housing and the rotor can rotate counter to one another during back-pedaling.
A freewheel which is fast and reliable in the introducing of driving force transferred from the rotor to the hub housing is known in the prior art from German utility model G 94 19 357.6. Meanwhile, friction losses are also relatively slight, if the user does not use the pedal.
This freewheel transfers forward rotor torque via a pair of toothed discs while the gear teeth are disengaged during back-pedaling.
A disadvantage of this freewheel is that a slight tilting of one of the toothed discs leads to greater wear on the more heavily stressed teeth so that durability is limited.
The task of the present invention is to provide a hub for a bicycle which meets the previously mentioned requirements and which, in particular, functions reliably, is easy to dismantle and which has a highly durable life.
This task is solved in accordance with the present invention by the object of claim 1, claim 26, or claim 27. Preferred embodiments of the invention constitute the subject matter of the subclaims.
The present invention provides a hub with high functional reliability and durability since the inventive freewheel contained in the hub achieves a reliable, durable and form-fitting connection during transferring of force while frictional losses occurring, for example during a downhill ride when not pedaling, are slight.
The hub according to the present invention has two bearing means as a front wheel hub and preferably four bearing means as a rear wheel hub. These bearing means are preferably configured as ball bearings, especially preferred is their configuring as grooved ball bearings, whereby it is especially preferable to use low-friction bearings and low-friction lubricants.
In addition to a hub axle which is rotatably mounted relative the hub housing, the hub according to the present invention also has a rotor mounted to be rotatable relative said hub axle and a freewheel device comprising at least two toothed discs arranged or switched between the rotor and the hub housing, said discs being pressed against each other by a pre-tensioning means and configured such that they transfer rotor torque in the direction of travel from the rotor to the hub housing. In a preferred embodiment, the tooth surfaces are arranged on a side surface and engage with one another upon transmission of torque.
The toothed discs are arranged substantially concentric to the hub axle and when assembled accordingly, the discs lie substantially in a plane perpendicular to an axial line of said hub axle, at least in the state of rest.
The toothed discs are of a floating mounting so that a tilting of said toothed discs perpendicular to the axial line relative this plane is possible during operation.
The hub according to the present invention has numerous advantages.
The use of two floating-mounted toothed discs has the advantage that a tilting of the first toothed disc causes a corresponding tilting of the second toothed disc such that the teeth arranged on said toothed discs are always reliably engaged with one another during a transmission of torque.
In a preferred embodiment of the inventive hub, said toothed discs are arranged adjacent to one another and urged together by means of at least one spring, whereby especially preferred is respective springs each exerting pressure against each outer side of the respective adjacent toothed discs. Configuring at least one of these springs as a coil spring is particularly preferred.
Such a configuration has many advantages since using two springs exerting pressure symmetrically from both sides onto adjacent toothed discs results in a symmetrical stressing and since using two springs allows for a quicker reaction at the outset. Consequently, the freewheel reacts faster to the introduction of driving force than conventional freewheels do.
In a further preferred embodiment, the toothed discs of the freewheel are configured to be relatively thin discs, their outer diameter amounting to between 20 and 40 mm; roughly 30 mm is preferred. Disc thickness amounts to between 4 and 12 mm; roughly 8 mm is preferred. A plurality of teeth are arranged on a side or disc surface, whereby the number of said teeth is  greater than 2, preferably between 4 and 60, and especially preferred between 6 and 48.
The quick and easy exchanging of toothed discs integrated in the hub is particularly preferred, as is the hub itself being readily opened without great exertion, in order to enable simple and feasibly daily cleaning, as is customary in professional cycling circles.
A greater number of teeth leads to a higher freewheel loading capacity, while friction is smaller with a lesser number of teeth.
When the corresponding toothed discs allow for simple and quick replacement, the user can choose between the individual advantages according to his or her own requirements for use so that toothed discs having a lesser number of teeth can be fitted for rides over even surfaces or at high speeds, while a greater number of teeth is more auspicious for uphill or cross-country rides since the loading capacity is greater.
In another preferred embodiment of the inventive hub, the teeth of the toothed discs are arranged on an annular section of the disc or side surface, wherein arranging the teeth on one of the outer annular areas of the toothed disc is especially preferred.
Two toothed discs are employed in a preferred embodiment of the inventive hub which are essentially similar or identical or manufactured in such a way that with two toothed-discs arranged with their tooth surfaces directly adjacent, at least a part of the teeth of one of said toothed discs engages in the recesses between the teeth of said second toothed disc, whereby the number of teeth of said two toothed discs may either be identical or different.
This constitutes a further advantage of the hub according to the present invention since the effect described above can be achieved by switching the toothed disc: employing a toothed disc with a lesser number of teeth reduces friction, employing a toothed disc with a greater number of teeth increases resistance.
The individual teeth are preferably configured to be asymmetrical. A long, flat incline having an angle of inclination of 5-30xc2x0, preferably at about 11xc2x0xc2x11xc2x0, forms one flank; the second flank of the tooth has an obtuse angle of about 100xc2x0 to the disc surface.
Upon a transmission of torque in the direction of travel, the toothed discs are pressed together by the pre-tensioning means and the steep flanks of the teeth transfer the torque.
When back-pedaling, the flat ascending sides of the teeth slide past each other, disengaging the toothed discs.
In a further embodiment of the hub according to the present invention, the side surfaces of the toothed discs are configured such that two contacting toothed discs are essentially in contact over a major portion of the disc surfaces.
In further embodiment of the inventive hub, the toothed discs are disposed with a plurality of projections distributed about the circumference of their outer surface in the radial direction which form a further radial gearing and which exhibit in the radial direction a triangular, rectangular, sinusoidal, trapezoidal or toothed-shaped cross-section in a plane of said toothed surfaces.
In another embodiment of the present invention, one of said toothed discs is essentially non-rotatably arranged in a substantially concentric bore or opening in the rotor arranged to align to the center of the hub in the corresponding assembly, and said rotor opening is configured such that said projections of said toothed discs extend into the radial recesses of said rotor.
In the hub housing of the corresponding assembly, a bore or opening is arranged in substantially concentric alignment toward the rotor in which a threaded ring comprising a bore is screwed into said hub housing, a toothed disc essentially non-rotatably arranged in said bore. Said bore in the threaded ring is preferably configured such that the projections of the toothed disc project into the radial recesses of said threaded ring.
These embodiments are particularly advantageous since one toothed disc is arranged non-rotatably in the rotor, while the other toothed disc is arranged non-rotatably in the hub housing. When contacting one another, a forward torque can be transferred from the rotor to the first toothed disc, from there to the second toothed disc, and from the second toothed disc to the hub housing.
The bore in the rotor and the bore in the threaded ring are preferably configured such that they are suited to receive only one toothed ring, effectively making it impossible for the toothed ring to switch from one of said holes to the other.
In all of the embodiments described thus far, the toothed discs are designed for a predefined maximum number of teeth. In a toothed disc having this maximum number of teeth, the teeth are evenly distributed circumferentially on the side surfaces, whereas while a toothed disc which has a lesser number of teeth has certain teeth omitted, the existing ones lie on the same grid as a toothed disc having the maximum number of teeth.
The circumferential spacing can vary from-tooth to tooth, at least in the case of a toothed disc having a number of teeth which cannot be determined from integral division of said maximum number of teeth.
A toothed disc with less teeth than the maximum can be fabricated in that certain teeth be omitted preferably in symmetrical distribution across the circumference, so that the circumferential spacing from one tooth to the next at these points is larger than at other points.
This configuration is of particular advantage since this measure allows toothed discs having almost any, even differing, numbers of teeth to be coupled with one another.
In a further embodiment of the hub according to the present invention, the rotor can be removed manually without the need for any special tool.
This is especially advantageous since it is particularly simple for a user to exchange gearwheels.
In a preferred embodiment of the inventive hub, the threaded ring is made of a metal alloy, preferably a light metal alloy; an aluminum alloy is especially preferred.
A light metal or an aluminum alloy is especially advantageous since this reduces the weight.
At least a part of the areas which transfer force in the hub may be, for example, additionally tempered through a surface treatment or similar measure. This is especially advantageous since it increases the service life and load capacity of the components.
A preferred embodiment of the invention provides a hub having high functional safety, since the sealing means provided in accordance with the invention prevents the entry of water and dirt into the hub body and especially prevents influx into the bearing means, or at least hinders same to the greatest possible extent.
The phrase xe2x80x9chinders to the greatest possible extentxe2x80x9d was chosen for the reason that a seal of this type can never be absolutely tight in the literal physical sense. The seal is, however, especially in the preferred configurations described in the following, designed such that infiltration of moisture and dirt is not possible during normal use nor during customary cleaning procedures.
According to a preferred embodiment, the sealing means is configured as a labyrinth seal. xe2x80x9cLabyrinth sealxe2x80x9d is to be understood as a seal in which the sealing surfaces moveable relative one another do not touch, but rather form a small seal gap inbetween. Said seal gap undergoes at least one change of direction, preferably several deflections, in fact preferably at an angle of about 90xc2x0, so that infiltration of liquid or dirt is basically impossible when a sufficiently constricted seal gap is chosen.
The use of a labyrinth seal has the advantage that the seal is not damaged or rendered ineffective even upon direct impact from a jet surge of water. Mountain bikes in particular are regularly cleaned after off-road use using a high pressure cleaner which sends water impacting the parts to be cleaned at a pressure of up to 150 bar. The multiple deflections to the labyrinth seal gap enable the water pressure created by the impact to be rapidly and reliably, degraded so that said pressure does not damage the seal and the water cannot penetrate to the bearings nor the hub interior.
In order to achieve a good sealing effect, it is preferable to have 3 or 4 deflections of roughly 90xc2x0. It is, however, also possible to provide fewer or more deflections.
According to another preferred embodiment, the sealing means is configured as an elastomer seal having an elastic lip and especially preferred is configuring the seal in essentially a V-shape. Hereby it is preferable to design the part which moves relative to the part to be sealed relatively thin so that an overlain elastic sealing surface or sealing lip exerting a relatively high pressure per surface area is attained which still generates only a low moment of friction.
According to an especially preferred embodiment, the sealing means comprises both a labyrinth seal as well as also an elastomer seal. In this case, it is preferable that the elastomer seal is downstream the labyrinth seal; it is however also possible that this order be reversed. Downstream refers to the elastomer seal being closer to the bearing and the labyrinth seal being farther away from the bearing and aligned toward the surroundings.
This results in the advantage as described above of greatly restricting the infiltration of water and dirt through the labyrinth seal even, for example, when employing a high-pressure cleaner, and that any possible residual amounts of fluid which could conceivably gain entrance to the hub through the labyrinth seal are prevented from penetrating on through to the bearing by the elastomer seal.
It is further preferred, particularly when making use of a labyrinth seal, to configure the sealing gap and all surfaces coming into contact with said sealing gap such that the centrifugal force generated by the rotation of the hub body can be used to expel any water which has penetrated the labyrinth seal back outside.
Also in the case of a combination of a labyrinth seal with a downstream elastomer seal, the surfaces of the seal gap and the surfaces of the elastomer seal are accordingly configured so that the conveying of infiltrated water back outward functions in a simple and reliable manner.
Particularly when using such a hub in competitive situations, it is absolutely essential that the hub be regularly dismantled despite good sealing effect in order to ensure that the bearings are in optimal condition. Complicated special tools are at times required to enable dismantling of conventional hubs, impeding regular maintenance.
The present invention therefore proposes structuring the hub such that it can be dismantled without the need for any tools, or at least for the most part without tools, or at least without the need for any special tools.
This is achieved according to a preferred embodiment of the invention in that the bearing is retained by a stopper element which itself is preferably retained only by friction. Said stopper element is preferably designed rotationally symmetrical to the axle itself and slid onto same whereby the retaining function is then generated by means of a frictional resistance between said stopper element and axle. The retaining function is preferably created by means of a gasket, preferably a conventional O-ring, which simultaneously affects a sealing relative stopper element and axle.
This configuration has the advantage that the stopper element with the sealing ring can be positioned on the axle and removed from same without the need for tools. At the same time, the corresponding configuration of the sealing ring allows for attaining a high moment of retention in order to hold the stopper element securely to the axle.
It is pointed out only for the sake of completeness that the stopper element in this configuration is structured such that it is retained at the inner side of the drop-outs in which the hub is held in the front wheel fork, respectively in the rear construction when the hub is in mounted state, and thus secured by the fitted screw connection, respectively quick-release means retaining the axle and hub in the drop-out.